LUREs is the correct answer.

LUREs (AtLURE1 peptides) are cysteine-rich defensin-like peptides secreted from synergid cells in the Arabidopsis ovule’s micropylar region, specifically attracting conspecific pollen tubes for precise guidance to the egg cell during double fertilization.​

Option Explanations

These options test knowledge of female gametophytic signals in pollen tube attraction, a key plant reproduction mechanism studied via semi-in-vivo assays and mutants like myb98.

• LeSTIG 1: Incorrect. This is a tomato (Solanum lycopersicum) stigma-specific cysteine-rich peptide involved in early pollen tube guidance on the stigma, not ovular micropyle attraction in Arabidopsis.​

• LUREs: Correct. AtLURE1.1–1.5 (CRP810_1 family) are synergid-expressed, six-cysteine defensin-like peptides that diffuse to the micropyle, bind pollen PRK6 receptors, and selectively accelerate conspecific pollen tubes, promoting reproductive isolation.

• GRP17: Incorrect. Glycine-rich protein 17 functions in Arabidopsis pollen wall patterning and exine formation, not ovule-based pollen tube attraction.​

• SCAs: Incorrect. Solanaceous cysteines (SCAs) are pollen tube chemotropically attractive peptides from tobacco/Nicotiana synergids, but not the primary micropylar signals in Arabidopsis (LUREs orthologs exist but are distinct).​

Cysteine rich peptide pollen tube attraction micropylar Arabidopsis questions target LUREs in NEET/GATE Botany, highlighting synergid signals for species-specific fertilization.

Pollen Tube Guidance Stages

Pollen tubes grow chemotropically: stigma (LeSTIG/SCAs), style (CRP810), ovule micropyle (LUREs). Synergids rupture post-attraction, releasing FERONIA-regulated signals.

LUREs Mechanism

AtLURE1 peptides (8 cysteines typical of DEFLs) evolve rapidly for species specificity; knockout reduces conspecific preference but not intraspecies fertility (XIUQIU peptides compensate).​

Exam Relevance

Distinguish: LUREs (Brassicaceae ovule), EA1 (maize synergid), NPA1 (non-defensin alternative). Mutants like lore1 confirm LUREs’ role.